Adjustable ultrasonic delay line with input and output transducer mounted on sliding block



y 3, 1966 T; J. GEOGHEGAN 3,249,900

ADJUSTABLE ULTRASONIC DELAY LINE WITH INPUT AND OUTPUT TRANSDUCER MOUNTED oN SLIDING BLOCK Filed Sept. 25, 1963 2 Sheets-Sheet l 6.0

-- //,1 l JHIIHH 'm .77 I i: 1 g 45 @2 1 35 56 l [I] I INVENTOR. Terrence J G60ghqgm; BY fiMm, aado y 1966 T. J. GEOGHEGAN 3,249,900

ADJUST ULTRASSEIIVRIC DE LAY LINE WITH INPUT AND OUTPUT MOUNTED ON SLIDING BLOCK 2 Sheets-Sheet 2 RANSDU Filed Sept. 25, l

66;, IYNVENTOR.

40 fir/6115 56 iff flab- 5 with 3,249,900 ADJUSTABLE ULTRASONIC DELAY LINE WITH INPUT AND OUTPUT TRANSDUCER MOUNTED ON SLIDING BLOCK Terrence J. Geoghegan, Hingham, Mass, assignor to Microsonics, Inc., Weymouth, Mass, a corporation of Massachusetts Filed Sept. 25, 1963, Ser. No. 311,503 11 Claims. (Cl. 333-30) embodiment thereof, is to provide an adjustable delay line characterized by a plurality of blocks of ultrasonic transmission media which are adapted to have relative sliding motion in contact with each other, one of which blocks mounts both an input transducer and an output transducer, and the other of which blocks carries reflecting surfaces which serve to reflect the ultrasonic wave or beam which is projected along an entering path from the input transducer, back over a return or reflected path to the output transducer.

In this regard, it is a further object to have the entering path of propagation and the reflected or return path of propagation both extend substantially in' parallelism to each other, and to effect the desired adjustments in delay timing by concurrently or simultaneously varying the length of the entering path and the length of the reflected or return path. 3

Another object directed to such latter embodiment of the invention is to provide a construction wherein the mounting block which mounts the two transducers has sliding motion along a sliding surface formed on the reflecting block which carries the reflecting surfaces, which sliding surface or interface extends obliquely at a substantial angle with respect to the reflecting surfaces, so that sliding adjusting motion of the mounting block along said sliding interface is effective to increase or decrease the over-all length of the entering path from the input transducer to the reflecting surfaces and the return path from the reflecting surfaces back to the output transducer.

Another object of the invention is to provide a construction in which the input transducer and the output transducer can always see each other, or be in permanent alignment with the entire effective face area of the other transducer, as reflected by Way of the reflecting surfaces, irrespective of what position of adjustment the mounting slide block occupies along the interface surface of the reflecting block. In the prior art where one transducer has bee-n mounted on one block and the other transducer has been mounted on another relatively slidable block, considerable difliculty has been encountered in maintaining this ability of the-two transducers to see each over a substantial range of adjustment.

Another object of the invention is to provide a construction in which the sliding interface surfaces between the two blocks are of substantially semi-cylindrical curvature, as distinguished from flat surfaces, with certain ultrasonic advantages which will be later described, together with the mechanical advantage of maintaining alignment during the sliding motion.

Other objects, features and advantages of the invention will be apparent from the following detailed description of certain preferred embodiments of the invention.

United States Patent In the accompanyingdrawings illustrating these embodiments:

FIGURE 1 is a front elevational view showing the stationary block and the slide block assembled upon a mounting panel or backboard;

FIGURE 2 is a substantially horizontal sectional view taken approximately on the plane of the line 2-2 of FIGURE 1;

FIGURE 3 is a side or edgewise elevational view taken on the plane of the line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary transverse sectional view taken approximately on the plane of the line 4-4 of FIGURE 1;

FIGURE 5.is a transverse sectionalview, on a larger scale, through the slide block and the stationary block, taken on the plane of the line 5-5 of FIGURE 1, showing the entering or admittance path of the ultrasonic wave propagated from the input transducer, and the reflected or return wave transmitted back from the reflecting surfaces to the output transducer;

FIGURE 6 is a front elevational view, part-1y broken away, illustrating a modified construction embodying sliding interface surfaces of semi-cylindrical cross section;

FIGURE 7 is a transverse sectional view taken on the plane of the line 7-7 of FIGURE 6; and

FIGURES 8 and 9 are side elevational and transverse sectional views showing the semi-cylindrical form of sliding interface surfaces adapted to another construction of adjustable delay line.

Referring first to the embodiment shown in FIGURES 1-5, the large stationary block which is provided with the reflecting surfaces is designated 20, and the coacting smaller slide block which mounts the two transducers is designated 22. Both of these blocks are composed of a suitable ultrasonic transmitting material, such as fused quartz or the like. In the exemplary embodiment shown, these two blocks are assembled on the front face of a mounting panel or backboard 24, by mounting apparatus which will be later described.

The large stationary block 20 is shown as being in the exemplary form of a right triangle having an apex angle X, an opposite side A, an adjacent side B and a hypotenuse C. The slide block 22, which is also shown as being of right triangular form, is mounted for sliding movement along the upper side of edge C of the stationary block 20. The corresponding edge C of the sliding block 22 constitutes the cooperating interface surface for 'sliding along the upper interface surface C of the large block. In the embodiment of the invention shown in FIGURES 1-5, these two interface surfaces C and C' are transversely flat. v Formed lengthwise along the adjacent or lower edge B of the large block 20 are parallel reflecting surfaces or facets 30 and 32 inclined at right angles to each other, as best shown in FIGURES 3 and 5. These reflecting facets are preferably formed by making the edge B of wedge shaped cross section extending the entire length of the block 20. These left and right hand reflecting facets 30 and 32 are both inclined at the same angle to the vertical and to the horizontal-Le. at 45 -so as to have an intervening angle of therebetween. As best shown in FIG- URE 5, the ultrasonic input beam IB propagated downwardly from the input transducer mounted on the slide block 22 intersects the left hand reflecting plane 30 substantially at its transverse center. This causes such beam to be reflected horizontally to intersect the right hand reflecting plane or facet 32 substantially at'its transverse center; from whence in turn this beam, now designated reflected beam RB, passes upwardly to the output transducer also mounted on the slide block. Mounted on' the upper surface B of the sliding block 22 are the input or transmitting transducer designated 34, and the output or receiving transducer designated 36. These transducers are preferably of piezoelectric crystal or ceramic type, but might be of other conventional construction. Mounted on the backs of the transducers are metallic absorbing plates 34' and 36 which function to absorb or prevent the return reflection of energy from the backs of their respective transducers, and which also function as terminal electrodes for establishing electrical connection with one side of the circuit connecting with the transducer. The other side of the circuit is connected to a conducting film extending underneath the transducer. Very thin flexible ribbon conductors 37 and 33 connecting with each transducer permit the sliding motion of the slide block 22 along the stationary block 20. The slope or angle of the surface B which supports the two transducers on the slide block 22 extends in exact parallelism with the slope or angle of the bottom edge B of the stationary block, whereby the line of propagation of the input beam IB from the input transducer will always lie in a plane which is perpendicular to the line of intersection of the planes of the reflecting surfaces 30, 32, so that the reflected beam RB will extend back in parallelism with the input beam IB and in the same said perpendicular plane for reception by the output transducer 36. This concept of mounting the two transducers on a single common slide block and reflecting the ultrasonic beam from the transmitting transducer back to the receiving transducer assures that the two transducers will always be in permanent alignment with each other so that the entire effective face area of the receiving transducer will always be able to see the entire effective face area of the transmitting transducer, irrespective of the delay time adjustment of the slide block along the upper interface surface C of the stationary block. The two transducers always remain in the same geometrical relationship to each other, and it is only the lengths of the input beam IB and of the reflecting beam RB that vary, and such variation occurs simultaneously in both beams.

The apparatus desirably utilizes ultrasonic waves of the shear type, which can be reflected from the reflecting surfaces and 32 with minimum disturbance or loss of energy. The interface surfaces C and C are provided with a coupling film diagrammatically illustrated in exaggerated thickness at 40 in FIGURE 5. This film should be as viscous as possible and look as nearly like a solid as possible, whereby the film will yield to slow pressure in shear caused by the relative sliding movement between the two prism blocks. The film should be as thin as possible, preferably less than .1 wave length, under which conditions the film will not cause any diffraction but the ultrasonic energy will pass through the film with a minimum of reflected energy. Compositions sold under the trade names of Vistac or Nonaq are illustrative of such viscous or unctuous films.

Referring now to one exemplary form of apparatus for mounting and adjusting the blocks 20 and 22, the large block 20 has its two sides A and B forced rigidly downwardly into clamping engagement against mounting bars 43 and 44 secured by screws 45 against the back panel 24. Downward clamping pressure is exerted against the top edge C of the stationary block through two rotatable cams 47 secured in their rotative positions of adjustment by clamping screws 48. The slide block 22 is anchored between the sides of a U'shaped carrier 49 which has its side flanges 50 extending downwardly and embracing the sides of the stationary block 20. Sliding adjustments are imparted to the slide block through a rotatable lead screw 52 on which threads a traveling nut or a follower 54. The end portions of the lead screw are journaled in hearing blocks 56, and one end of the lead screw carries a knurled knob 58. The top surface of the traveling nut 54 has sliding guided abutment aaginst the underside of a guide bar 6% secured tothe back panel. The endwise motion of the traveling nut 54 is transmitted to the carrier 49 by a downwardly extending pin 62 projecting from the nut or follower down through an aperture in the top of the carrier 49. The carrier member 49 is made capable of limited rocking movement relative to the nut or follower 54 by the interposition of two balls 64, 64 therebetween, these balls seating in shallow spherical cavity inserts 66 set into the top of the carrier 49.

From the foregoing description, it will be seen that as the slide block 22 is moved along the interface surface C of the stationary block 20 in the performance of an adjusting operation, there will be a simultaneous variation in the lengths of both the input beam IB and of the reflected beam RB for adjusting the delay time, the lengths of the beams being increased and the delay time lengthened as the slide block 22 is moved toward the right, and the lengths of the beams being decreased and the delay time shortened as the slide block is moved toward the left. Thus the device gives a continuous variation in delay time over a substantial range. And, it should be noted that the two transducers 34 and 36 continue to see the entire surface area of each other in each and every position of adjustment. The fact that the oblique mounting angle of the two transducers 34, 36 on the sloping top surface B of the slide block 22 is exactly the same as or parallel with the oblique angle of the reflecting planes 30 and 32 along the sloping bottom B of the stationary block 20 insures that the path of the reflected beam RB will always be parallel with the input beam IB.

FIGURES 6 and 7 illustrate a modified construction in which the mating surfaces of the two blocks 20 and 22 are in the form of cylindrically curved matching interfaces designated CC and CC. As shown in FIGURE 7, the input beam IB passes downwardly through the convex and concave interfaces on its way to the first reflecting surface 30, and the reflected beam RB in passing upwardly from the second reflecting surface 32 passes through these concave and convex interfaces in reverse sequence. The coupling film 40 is provided between these two semicylindrical interfaces. These semi-cylindrical surfaces afford certain ultrasonic advantages. For example, the ultrasonic energy is a mechanical vibration which has a plane wave front. If this plane wave front encounters a plane type of discontinuity wherein all portions of the wave front encounter the plane discontinuity substantially simultaneously, then there will be substantial reflection of the ultrasonic energy, which reflection will be in the form of a Well defined energy front. However, this effect is avoided or minimized by the use of the curved semi-cylindrical interfaces, whereby the wave front encounters or goes through a gradual transition by striking one part of the curved surface ahead of another part. A further mechanical advantage of these semi-cylindrical interfaces resides in the self-aligning feature of the two surfaces.

In FIGURES 8 and 9 I have shown the above feature of the semi-cylindrical interface surfaces embodied in a prior construction of an adjustable delay line, particularly of the type wherein the stationary block carries one of the transducers and the slide block carries the other transducer. In this construction, the stationry block designated 26a and the slide block designated 22a are also preferably composedof fused quartz or any other material adapted to transmit ultrasonic vibrations efliciently. The input transducer 34a is preferably mounted at one end of the slide block 22a, and the output transducer 36a is preferably mounted at the opposite end of the stationary block 20a. Both of these transducers are shown as being obliquely inclined at approximately the same angle relatively to the line of sliding movement between the blocks, in order to enable the two transducers to continue to see as much of each other as possible through the quartz material as the slide block is slid endwise relatively to the stationary block. I propose to modify this conventional construction by constructing the mating surfaces of the two blocks of semi-cylindrical form, as shown in FIGURE 9. In this construction the stationary block a is formed with the concave interface surface CC, and the slide block is formed with the convex interface surface CC. These interface surfaces have a lubricating film between. The semi-cylindrical curvature of these two interface surfaces give to this latter construction the same ultrasonic advantages referred to above, and also the mechanical advantage of self-alignment. The right hand end of the stationary block 20a is preferably curved and coated with sound absorbing material as indicated at 48, and the left hand end of the slide block 22a is likewise curved and provided with sound absorbing material as indicated at 56, whereby to minimize reflections in the blocks.

While I have illustrated and described what I regard to be the preferred embodiments of my invention, nevertheless it will be understood that such are merely exemplary, and that numerous modifications and rearrangements may be made therein Without departing from the essence of the invention.

I claim:

1. In an adjustable delay line, the combination of a stationary block and a slide block both composed of ultrasonic transmitting media, cooperating straight line interface surfaces on said two blocks along which said slide block is adapted to have sliding movement relatively to said stationary block, an input transducer and an output transducer both mounted on said slide block and directed toward said interface surfaces, and relatively long narrow intersecting reflecting planes on said stationary block extending at an oblique angle relatively to said interface surfaces to reflect ultrasonic beams transmitted through said blocks from said input transducer back to said output transducer, the movement of said slide block along said interface surfaces being in a line oblique to the line of intersection of said reflecting planes.

2. In an adjustable delay line, the combination ofa stationary block and a slide block both composed of an ultrasonic propagation medium having substantially the characteristics of fused quartz, cooperating straight line interface surfaces on said two blocks along which said slide block is adapted to have sliding movement relatively to said stationary block, a rotatable lead screw and traveling nut operatively arranged to effect such sliding adjustment of said slide block along said stationary block, an input transducer and an output transducer both mounted on said slide block at an angle extending obtusely relatively to said interface surfaces, and two relatively long narrow intersecting contiguous reflecting planes disposed at right angles to each other and extending along said stationaryblock at an angle which has the same oblique relationship to said interface surfaces as the mounting angle of said input and output transducers, the movement of said slide block along said interface surfaces being in a line oblique to the line of intersection of said reflecting planes.

3. In an adjustable delay line, the combination of a first block and a second block both composed of ultrasonic transmission media, cooperating interface surfaces on said two blocks along which one of said blocks is adapted to have sliding movement relatively to the other block, an input transducer and an output transducer both mounted on the slidable one of said blocks, two relatively long parallel reflecting planes on the other of said blocks, said reflecting planes extending at an oblique angle to said interface surfaces, whereby relative sliding movement between said blocks along said interface surfaces operates to vary the reflected path length of ultrasonic beams transmitted from said input transducer to said reflecting planes and thence reflected back to said output transducer, said cooperating interface surfaces being of matching semi-cylindrical cross section, one of convex curvature and the other of concave curvature, whereby a penetrating wave front passing through said interface surfaces goes through a gradual transition by striking one part of the semi-cylindrical curved surface ahead of another part.

4. The combination defined in claim 2 wherein said straight line interface surfaces are both of semi-cylindrical cross section, one of convex curvature and the other of matching concave curvature.

5. In an adjustable delay line, the combination of a mounting panel, a stationary block mounted on. said panel, a slide block adapted to have sliding motion along said stationary block, said two blocks being composed of material acoustically suitable for conducting sound in the ultrasonic range, an interface surface along the upper edge of said stationary block and a cooperating interface surface along the lower edge of said slide block, along which said slide block is adapted to have sliding movement relatively to said stationary block, mounting bars on said mounting panel adapted to receive two angularly disposed lower edges of said stationary block, eccentric cam means bearing against the upper edge of said stationary block for forcing said lower edges downwardly against said mounting bars, one of said lower edges extending at an oblique angle relatively to said top edge and having two reflecting facets formed longitudinally along said lower edge, said reflecting facets being at right angles to each other transversely of said stationary block, said slide block having an upper mounting surface extending in parallel relation to said reflecting facets, an input transducer and an output transducer mounted in parallel relation on an upper mounting surface of said slideblock, said input transducer propagating an ultrasonic beam downwardly through said slide block, through said interface surfaces and through said stationary block to said reflecting facets, from whence said beam is reflected back through said stationary block and through said interface surfaces and said slide block in parallel relation to said propagated beam for reception at said output transducer, a lead screw mounted in bearings carried by said mounting panel and extending substantially parallel with said interface surfaces, a traveling nut traveling along said lead screw, a carrier embracing said slide block, pin means transmitting the traveling motion of said nut to said carrier, and balls mounted between said travelingnut and carrier for permitting limited tilting motion therebetween. 6. In an adjustable delay line, the combination of a stationary blockanda slide block, both composed of ultrasonic transmission media, cooperating straight line interface slide surfaces on said two blocks along which said slide block is adapted to have sliding movement relatively to said stataionary block, an input transducer and an output transducer both mounted on said slide block and directed obliquely in parallel relation toward said interface surfaces, two relatively long narrow reflecting surfaces along another edge of said stationary block, said reflecting surfaces intersecting each other at along a line of intersection extending the lengths of said reflecting surfaces, and means for moving said slide block along said interface surfaces in a plane generally parallel to the lengths of said reflecting surfaces and in a line oblique to said line of intersection, whereby a substantially constant signal aperture is maintained between said input and output transducers in the various shifted positions of said slide block along said slide surfaces. 7. In an adjustable delay line, the combination of a mounting panel, a stationary block mounted on said panel, a slide block adapted to have sliding motion along said stationary block, said two blocks being composed of material acoustically suitable for conducting sound in the ultrasonic range, an interface surface along the upper edge of said staationary block and a cooperating interface surface along the lower edge of said slide block along which said slide block is adapted to have sliding movement relatively to said stationary block, one of said lower edges extending at an oblique angle relatively to said top edge and having two reflecting facets formed longitudinally along said lower edge, said reflecting facets being at right angles to each other transversely of said stationary block, said slide block having an upper mounting surface extending in parallel relation to said reflecting facets, an

input transducer and an output transducer mounted in parallel relation on an upper mounting surface of said slide block, said input transducer propagating an ultrasonic beam downwardly through said slide block, through said interface surfaces and through said stationary block to said reflecting facets, from whence said beam is reflected back through said stationary block and through said interface surfaces and said slide block in parallel relation to said propagated beam for reception at said output transducer, a lead screw mounted in bearings car ried by said mounting panel and extending substantially parallel with said interface surfaces, a traveling nut traveling along said lead screw, a carrier embracing said slide block, pin means transmitting the traveling motion of said nut to said carrier, and balls mounted between said traveling nut and carrier for permitting limited tilting motion therebetween.

8. In an adjustable delay line apparatus of the class described, the combination of a stationary block and a slide block, both composed of ultrasonic transmission media, cooperating straight line interface slide surfaces on said two blocks along which said slide block is adapted to have sliding movement relatively to said stationary block, a transmitting transducer and a receiving transducer both mounted on said slide block and each having a viewing area directed obliquely in parallel relation toward said interface surfaces, two relatively long narrow reflecting surfaces along another edge of said stationary block, said reflecting surfaces intersecting each other along a line of intersection which extends the length of said reflecting surfaces and at an angle oblique to said interface surfaces, said transmitting transducer propagating an ultrasonic beam downwardly through said slide block,

I through said interface surfaces and through said stationary block to said reflecting surfaces, from whence said beam is reflected back through said stationary block and through said interface surfaces and said slide block in parallel relation to said propagated beam for reception at said receiving transducer, and means for moving said slide block along said interface surface, said oblique relation of the line of movement of said slide block and the line of intersection of said reflecting surfaces maintaining the entire transmitting area of said transmitting transducer in constant view of the entire receiving area of said receiving transducer over the entire range of adjusting movement of said slide block along said interface surfaces.

9. In an adjustable delay line, the combination of a stationary block and a slide block, both composed of ultrasonic transmission media, cooperating straight line interface slide surfaces on said two blocks along which said slide block is adapted to have sliding movement relatively to said stationary block, input and output means mounted on one of said blocks, each of said input and output means having a predetermined viewing area, two relatively long narrow reflecting surfaces located on the other one of said blocks, said reflecting surfaces having sides intersecting each other to define a line of intersection for the length of the reflecting surfaces, and means for moving said blocks along said interface sur- 2% faces on a line which extends obliquely to the line of intersection of said reflecting surfaces to provide a substantially constant viewing area between said input and output means in each of the various shifted positions of said slide block along said slide surfaces.

10. In an adjustable delay line, the combination of a first block and a second block both composed of ultrasonic transmission media, transducer means on said first block including transmitter means having an effective viewing area for transmitting an ultrasonic beam to said second block, and receiving means having an effective viewing area for receiving said beam after reflection from said second block, cooperating interface surfaces on said two blocks along which one of said blocks is adapted to have sliding movement relative to the other block, reflecting means on said second block comprising a first and a second reflecting'surface disposed in angular, facing relation with each other to form a line of intersection at one edge thereof which extends at an oblique angle to said interface surfaces, and means for effecting relative movement of said two blocks along said interface surfaces to provide a constant ratio between the effective viewing areas of said transmitter and receiver means through the entire length of relativemovement of said blocks.

11. In an adjustable delay line, the combination of a first block and a second block both composed of ultrasonic transmission media, input means on said first block having a viewing area for transmitting an ultrasonic beam to said'second block, and receiving means on said first block having a viewing area for receiving said beam after reflection from said second block, cooperating interface surfaces on said two blocks along which one of said blocks is adapted to have sliding movement relative to the other block, reflecting means on said second block comprising a first and a second reflecting surface disposed in angular, facing relation with each other to form a line of intersection at one edge thereof which extends at an oblique angle to said interface surfaces, and means for effecting relative movement of said two blocks along said interface surfaces, said one reflecting surface being disposed in each position of said blocks to reflect the input beam to said second reflecting surface, and said second reflecting surface being disposed in each position of said blocks to reflect the beam to said receiving means, the ratios of the viewing area of the input and receiving means to each other being constant throughout the entire length of relative movement of said blocks, the path of reflection of said beam by said second reflecting means to said receiving means in said second block being substantially parallel to the input path of said beam to said first reflecting means.

References Cited by the Examiner UNITED STATES PATENTS 2,659,053 10/1953 Johnson 333-30 2,996,687 8/1961 Wright 33330 3,103,640 9/1963 Lockhart 333-30 3,146,412 8/1964 Wright 333-30 HERMAN KARL SAALBACH, Primary Examiner. 

1. IN AN ADJUSTABLE DELAY LINE, THE COMBINATION OF A STATIONARY BLOCK AND A SLIDE BLOCK BOTH COMPOSED OF ULTRASONIC TRANSMITTING MEDIA, COOPERATING STRAIGHT LINE INTERFACE SURFACES ON SAID TWO BLOCKS ALONG WHICH SAID SLIDE BLOCK IS ADAPTED TO HAVE SLIDING MOVEMENT RELATIVELY TO SAID STATIONARY BLOCK, AN INPUT TRANSUCER AND AN OUTPUT TRANSDUCER BOTH MOUNTED ON SAID SLIDE BLOCK AND DIRECTED TOWARD SAID INTERFACE SURFACES, AND RELATIVELY LONG NARROW INTERSECTING REFLECTING PLANES ON SAID STATIONARY BLOCK EX- 